Leak detector

ABSTRACT

A handheld-sized, single-hand-holdable, single-hand-operable battery-powered gas leak detector that draws in a sample of ambient air for detecting the presence of a gas by sensing changes in infrared (IR) energy between an IR emitter and an IR sensor when the gas is in the space between the IR emitter and the IR sensor. An algorithm is used that triggers detection of a gas when the change in IR energy between the IR emitter and the IR sensor is more rapid than the thermal drift of the IR sensor, and the detector design allows for IR energy within a wide range of approximately 0.4 micrometers to approximately 20 micrometers to pass into the air being sampled.

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

BACKGROUND OF THE INVENTION

The technical field of invention relates to a leak detecting device fordetecting presence of a gas. More particularly, the present inventionpertains to a hand-held, single-hand-sized leak detecting device forgeneral hazardous gas detection or air-borne sampling and detecting thepresence of a specific gas.

Several different designs of leak detectors have been disclosed invarious publications. The different designs are directed to providepotential solutions to particular problems. For example, US patentapplication publication no. US 2015/0028209 by Harju et al. (“Harju”),published Jan. 29, 2015, with assignee identified as FieldpieceInstruments, Inc., discloses a refrigerant gas leak detector thatincorporates a two-part unit—a first (handle) portion consisting of agas sampling chamber and an infrared (IR) optical detector specific todetecting bandpass filtered IR energy within the range of 7 to 14microns, and a second portion (presumably managed with the user's secondhand, with the user's first hand holding the first/handle portion)connected to the first portion by a flexible tube, the second portionconsisting of a suction pump, signal processing, and battery powercomponents. The two-part design in Harju is disclosed as a solution tothe problem of false triggering due IR emitter sensitivity to thevibration of the pump motor and to IR emitter sensitivity to pressurefluctuation from the pump. The two-part design places the IR emitter inthe handle portion and the pump motor in the second portion, connectedby three feet of flexible hosing, thereby dampening pump vibration andpressure fluctuation.

Harju also discloses an embodiment of an IR leak detector that utilizesa single housing for all the leak detector components—including the gassampling chamber, the optical detector with bandpass filter for allowingIR energy within the range of 7 to 14 microns to pass (and attenuatingenergy outside of that range) between the IR emitter and IR sensor, thesignal processing components, and (presumably, but not shown in figuresor clearly described) the suction pump, and associated battery power.Harju discusses detection of refrigerants that absorb wavelengths of IRlight primarily in the 8-10 micron range, and preferred detector designshaving a 7 to 14 micron bandpass IR filter formed integrally with the IRsensor, which Harju discloses as being directed to the detection ofrefrigerants such as hydrofluorocarbons (HFCs), hydrochlorofluorocarbons(FCFCs), and chlorofluorocarbons (CFCs).

Harju further discusses disclosures in Williams, I I et al. U.S. Pat.No. 7,022,993 and Williams, I I et al. U.S. Pat. No. 6,791,088(collectively, “Williams”), both reexamined (with all claims in the '088patent cancelled and claims 2-3, 6-7, and 9 determined patentable in the'993 patent) and having the assignee identified as Twin RiversEngineering, Inc., that describe gas leak detector designs incorporatingoptical filtering to block IR energy that is absorbed by water vapor andother gases at wavelengths that are 6 microns and below, to reduce falsetriggering. The Williams gas leak detector designs include a (first)filter next to the IR emitter for blocking IR energy from approximately6 microns down through the sampling chamber, and another (second) filterin front of the IR sensor for allowing a selected IR energy range ofapproximately 8 to approximately 10 microns to pass through the samplingchamber, with the IR sensor arranged for detecting resultant IR energyfrom the first filter and the second filter. Like Harju, Williamsdiscloses designs directed to gas leak detection of HFCs, HCFCs, andCFCs. In addition, Williams lists numerous other compounds that can bedetected, although Williams does not disclose the specific designchanges needed for detection of such additional compounds. Theadditional compounds listed in Williams include: refrigerant blends,propane, methane, gasoline, ammonia, acetone, benzene, bromine, carbondioxide, carbon monoxide, chlorine, fluorine, hydrogen sulfide, isobutylalcohol, isopropyl ether, pentane, sulfur dioxide, sulfur hexafluoride,trichloroethane, vinyl acetate, vinyl bromide, and xylenes.

Both the Harju and Williams designs provide audible indication for gasleak detection. Harju includes a beeper that provides an audible signalwhen a leak is detected. The Williams design includes an audio output tothe detector for emitting an audio signal from a detected leak, theaudio output having a 1 Hz chirp rate that digitally shifts to a 2 Hzchirp rate upon detection of the gas leak. The chirp rate increasesabove the 2 Hz rate in proportion to the size of the gas leak beingdetected.

Both the Harju and Williams designs include gas leak detection by way ofsensing a gas within a chamber between an IR emitter and an IRsensor/detector, with signals from the IR sensor/detector used todetermine presence of a target gas to be detected. Harju disclosessignal processing circuitry in very general terms that include circuitryfor receiving and amplifying IR sensor output signals that are theninput to a central processing unit (CPU). The CPU receives controlsignals from an external controls device and provides output signals toa display, status indicator lights, and to a beeper for an audiblesignal when a gas leak is detected. The Williams gas leak detectorincludes a signal detection accumulator in the detector with a forwardbiased detector circuit, and a zero circuit in the detector referencedto approximately a circuit ground instead of referenced between supplyrails. Signals from the detection accumulator are directed to LEDdrivers for LED display and to a tone chirp rate generator for driving apiezo speaker.

Another IR instrument designed for the detection of contaminants inambient air is the INFRARAN (trademark) specific vapor analyzer by WilksEnterprise, Inc. (“Wilks”). The Wilks analyzer is a portable device andis larger (at 15″×7.3″×7.5″) and heavier (at 18 pounds) than either ofthe much smaller hand-held designs disclosed in Williams and Harju.Operation is two-handed, with one hand for carrying the 18 pound mainbody, and the other hand positioning an air sampling wand connected to aflexible tube leading back to the main body. The Wilks design providesan analyzer that can be purchased to measure a compound that has anabsorption band in the IR range from 2.5 to 14.5 microns. The designuses fixed bandpass filters in the IR optics. An integral air pump drawsthe sample gas into a cell (chamber) having two mirrors, one on each oftwo opposite sides of the cell. An IR emitter and an IR detector arepositioned aft of one of the mirrors on one side of the cell, withsupporting amplifier and signal processing circuitry for receivingoutput from the IR detector, and a CPU, control inputs, display outputs,and (battery or AC) power management circuitry. The air pump draws thesample into the cell, and the sample absorbs the IR energy from the IRbeam (that is bounced back and forth within the cell between the twomirrors). The IR detector measures the amount of energy absorbed at theselected wavelength, and the microprocessor converts it into aconcentration (ppm or percent) for display. The Wilks product brochurelists the following as gases that can be detected and measured: acetone,carbon dioxide (absolute), carbon monoxide, carbon tetrachloride,desflurane, general hydrocarbons (hexane), isoflurane, isopropylalcohol, methylene chloride, nitrous oxide, perchloroetylene, R 114, R12, R 134A, R 236 fa, sevoflurane, sulfur hexafluoride, and toluene.

Each of the existing IR gas detector designs has disadvantages in termsof cost, complexity of design, ease of use, range of IR energy detected,method of audible alarm, form factor and ergonomics of the device,design aesthetics, and/or other factors. What is needed are designs fora hand-held, single-hand-sized leak detecting device for generalhazardous gas detection or air-borne sampling and detecting the presenceof a specific gas that address one or more disadvantage of existingdesigns.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL DRAWINGS

For a more complete understanding of the present invention, the drawingsherein illustrate examples of the invention. The drawings, however, donot limit the scope of the invention. Similar references in the drawingsindicate similar elements.

FIG. 1 illustrates a front view of a hand-held, single-hand-sizedinfrared (IR) gas leak detector, according to various preferredembodiments.

FIG. 2 illustrates a back view of the gas leak detector in FIG. 1,according to various preferred embodiments.

FIG. 3 illustrates a cutaway side view of the gas leak detector in FIG.1, according to various preferred embodiments.

FIG. 4 is a functional block diagram of an infrared (IR) based gasdetector, according to various embodiments.

FIG. 5 is a schematic of circuitry comprising the microcontrollersection of the main circuit board for the gas leak detector of FIG. 1,according to preferred embodiments.

FIG. 6 is a schematic of circuitry comprising the power section of themain circuit board for the gas leak detector of FIG. 1, according topreferred embodiments.

FIG. 7 is a schematic of circuitry comprising the sensor section of theseparate, sensor-end-of-the-bench circuit board for the gas leakdetector of FIG. 1, utilizing a pyro-electric type detector, accordingto preferred embodiments.

FIG. 8 is a schematic of circuitry comprising the sensor section of theseparate, sensor-end-of-the-bench circuit board for the gas leakdetector of FIG. 1, utilizing a thermopile type detector, according topreferred embodiments.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the preferredembodiments. However, those skilled in the art will understand that thepresent invention may be practiced without these specific details, thatthe present invention is not limited to the depicted embodiments, andthat the present invention may be practiced in a variety of alternateembodiments. In other instances, well known methods, procedures,components, and systems have not been described in detail.

Preferred embodiments comprise a handheld-sized, single-hand-holdable,single-hand-operable battery-powered gas leak detector that draws in asample of ambient air for detecting the presence of a gas by sensingchanges in infrared (IR) energy between an IR emitter and an IR sensorwhen the gas is in the space between the IR emitter and the IR sensor. Apreferred ergonomic form-factor for such a gas leak detector isillustrated in FIGS. 1, 2, and 3, with FIG. 1 showing a front side ofsuch device 10, FIG. 2 showing a back side, and FIG. 3 depicting a sidecutaway view revealing various internal components of such device 10.

In one embodiment, the IR gas detector 10 comprises an optical devicereferred to as the “bench,” housed within the space 70 and supported byan electronic circuit board 62 that is capable of discriminating changesin the thermal sensor section of the bench. The bench preferablycomprises a hollow sample tube 140 as diagrammed in FIG. 4, that iscapped and sealed at each end by a housing that mounts an infraredradiation source (IR emitter 150) and an IR optical filter 190 at oneend and a thermal sensor 160 with two IR optical filters 170, 180 at theother end. The bench air path is preferably sealed from the emitter andsensor by the IR filters which slows undesirable heat transfer byconvection from the sample air stream. Because the emitter 150 may reachtemperatures that could ignite many gasses, a sealed IR filter/emittercombination also provides isolation from combustible gasses as they passthrough the bench.

From the sample tube 140 there are preferably two small tubes, oneconnecting to the detector air sample inlet and the other to a small airpump 120. The pump provides suction (for example, at a flow rate of 100cc/min.) for the air sample that passes through the bench. The inventordiscovered it is possible to deplete the gas from a very small leak iftoo much air is taken in, and the inventor determined an intake flowrate of 100 cc/minute is preferred. The gas sampling inlet 100 ispreferably a flex tube for positioning its tip into hard to reachplaces. The inventor determined the inside diameter of the inlet tube100 is preferably small so as to accelerate/speed the passage of thesample air or air and gas mix. In addition to a small inside diameter ofintake tube 100, there is preferably a moisture blocking filter withinthe inlet tube 100 that prevents contamination from reaching the IRoptics within the bench. In one embodiment, a visible filter media isused in the intake tube 100 that turns blue when it becomes wet, lettingthe user know of the contaminants in the sample air.

The detection process preferably comprises focusing the IR emitter 150beam on the IR detector 160, whereupon the sensor 160 reacts to heatgenerated by the IR beam. In operation, and in accordance with preferredembodiments, with a sample nozzle 100 intaking “clean air”, the thermalsensor stabilizes and the gas detector 10 generates a “normal” audiosignal every two seconds to indicate that the gas detector 10 has warmedup and is not sensing a change in the air passing through the bench.Preferably the sensor output signal only responds to a change intemperature at the sensor element. In practice, as discovered by theinventor, there are two primary causes of a change in temperature at thesensor. First is the amount of IR radiation that is shining on thesensor element. The second primary cause is undesirable and is a resultof the environment, including the temperature of the sample air streamand housing, and causes the thermal sensor to drift.

When air passing through the bench contains a detectable gas, the gasmolecules absorb some of the IR radiation and convert the absorbed IRenergy to kinetic energy. The result is a cooling of the IR sensor asless IR energy strikes the sensor. The amount of absorption is afunction of the gas type and the concentration of the gas, and theabsorption increases as the natural log of the concentration. When thereduction of heat reaches the sensor 160, the device 10 preferablygenerates a signal proportional to the cooling, and the device 10preferably stops the “normal” tone and generates a high pitched audiotone to indicate detection of gas. Non-symmetrical gas molecules willabsorb IR energy at various wavelengths relative to their chemistry anddensity. Different gasses absorb IR energy at different IR wavelengths,and the amount of absorption is different for different gasses.

In various embodiments, different IR filters may be used to tune the gasdetector 10 for various gas compounds. Preferably, the IR opticalfilters in the device 10 limit the wavelength of IR energy that passesthrough the bench to approximately 1-20 micrometers. Additionally, theIR filters (along with the air space between the filters and the emitteror sensor) provide significant thermal isolation for the IR emitter 150and the thermal sensor 160 from the stream of air passing through thebench sample tube 140. The cooling of the thermal sensor 160 when a gasenters the bench, the inventor determined, is a small fraction of adegree. The “thermal sensor can,” the inventor discovered, is assensitive to thermal changes as the sensor element. Therefore, theinventor determined, the housing preferably needs to maintain a stabletemperature. And the inventor further discovered that the particulartemperature of the housing does not matter as long as the temperature ofthe housing is maintained as stable as possible. In practice, as theinventor discovered, there is always some thermal drift.

The inventor determined that it is practically impossible, or at leastunnecessary, to control the thermal drift of the environment that thegas detector 10 is exposed to, and the thermal drift of the sensorhousing is preferably slow compared to the reaction inside the bench togas entering the sample tube 140. In one embodiment, double IR opticalfilters 170, 180 provide the additional function of reducing thermaldrift of the sensor housing. The inventor determined adequate insulationprovided by the plastic housing of the gas detector 10 is preferred, tofurther reduce thermal drift of the sensor housing.

Additionally, the inventor discovered simple bending of the benchslightly will cause signal changes that could be interpreted as a gasdetection signal, so mounting the bench so as to minimize distortion ofthe bench when normally handled, is preferred. In one embodiment, afloating mounting of the bench is used. For example, the space 70 withinwhich the bench is preferably disposed within the plastic housing asshown in FIG. 3 having back and front sides 66, 62 and bottom and topends 24, 22 in a way that maintains the rigidity of space 70, with space70 floatably secured within the plastic housing so that distortions ofthe plastic (outer) housing do not transfer to distortions of the space70 comprising components of the bench. In another embodiment, theinventor determined one way to obtain sufficient stability of the benchstructure is to cast the bench into the molded housing of the gasdetector 10. For example, the space 70 and components comprising thebench may be integrally molded into the rigid plastic housing of the gasdetector 10 shown in FIG. 3.

The power for the IR gas leak detector 10 preferably comprises batteries64, such as four (4) AA alkaline batteries accessible via a batterycover 20 on the back side 18 of the device. The inventor determined themain power draw of the leak detector 10 is the IR emitter 150, followedby the air pump 120. Battery voltage is preferably regulated by bothlinear and switching regulators.

FIGS. 5, 6, 7, and 8 are exemplary schematics for circuitry comprising agas leak detector such as device 10, according to various embodiments.FIG. 5 shows a circuitry labeled “X214M” comprising the microcontrollersection of the main circuit board 62 for device 10, and FIG. 6 showscircuitry labeled “X214P” comprising the power section of the maincircuit board 62 for device 10. Both the microcontroller section andpower section circuitry are preferably located on the main circuit board62, and circuitry comprising the sensor section is preferably on aseparate circuit board located at the sensor end of the bench. FIG. 7shows circuitry comprising the sensor section of the separate,sensor-end-of-the-bench circuit board for the gas leak detector 10,utilizing a pyro-electric type detector. And FIG. 8 shows circuitrycomprising the sensor section of the separate, sensor-end-of-the-benchcircuit board for the leak detector 10, utilizing a thermopile typedetector (instead of the pyro-electric type detector).

Additional circuitry (not completely shown in the schematics shown inFIGS. 5-8) is preferably included to provide a tactile feedback (i.e.vibration) for the user, to indicate a gas detection event. Preferably,the level of vibration output increases as the gas concentrationdetected increases. The larger the gas leak, the more/stronger vibrationof the device 10 output to the user.

The sensor section circuitry preferably includes a 24 bit analog todigital converter that samples the (pyro-electric or thermopile type)thermal sensor signal. The can that mounts the pyro-electric sensor, forexample, is preferably sealed with an integral IR optical filter window.Different IR filters may be used to tune the detector for various gascompounds. The sensor housing preferably also mounts a second filterwith an insulating washer between them, providing the spacing to ensurean insulating air gap between the sensor can and the second filter. Theinventor discovered that the washer minimizes the heat transfer from thesecond filter to the sensor can, thereby further improving sensorperformance. The inventor determined that successful gas detection isimproved when the thermal drift of the sensor is slow as compared to theIR absorption caused by the gas concentration. The inventor discoveredthat this allows the gas detection algorithm to ignore the slow driftthat is normal for the sensor and to detect the rapid decrease in IRheating of the sensor element caused by a gas entering the bench.

Turning back to FIGS. 1-3, several innovative features of a single-handsized gas detector 10 are illustrated. As shown, the detector 10preferably comprises a main body or plastic housing having alongitudinal length from a bottom or rear most surface 24 to a top orforward most surface 22, and having a transverse width from a leftsurface 26 to a right surface 28. In one embodiment, the longitudinallength 22-24 is approximately 171.5 mm, and the width left to right26-28 is approximately 69.8 mm. Extending forward from the main body isthe intake tube or intake probe 100 (shown partially). Extending outwardfrom each side near the forward portion of the device 10 where an outputdisplay 12 is positioned, are, as shown, right and left extensions, 30and 32, respectively, configured and sized for holding the device 10 invarious device holding accessories (not shown). On the front centerportion of the device 10 are positioned one or more (preferably four)navigation buttons 14 for use in operating the leak detector/device 10.In some embodiments, the navigation buttons 14 are usable in connectionwith output presented by the display 12 to access and select from menuoptions.

To aid in handling the device 10 and for improved and unique aestheticsof the device 10, a rubber or similarly grip improving material 16 ispreferably formed around the sides and top and bottom surfaces, asshown. In one embodiment, the grip material 16 covers the sides, top,and bottom, and leaves the front and rear (back side 18) portions of themain body uncovered. In preferred embodiments, the grip material 16areas and the uncovered main body portions are of contrasting colors.For example, the grip material 16 may be black or dark grey, and theuncovered main body portions may be a contrasted color such as yellow,or orange, or another contrasted color.

Also included for improved handling and to aid with using the device 10with a single hand, are side grip ridges 46, 48, 50, 60, 52, 54, 56, and58. The side grip ridges preferably comprise matching pairs of right andleft ridges, for example ridges 52 and 46, 54 and 48, 56 and 50, and 58and 60. The side grip ridges also provide a unique and iconic patternthat may provide a source identifying (or trademark) function for thedevice. For example, the pattern—two ridges 46, a larger section 34,three ridges 48, a large section 36, three ridges 50, a large section38, and finally two ridges 60—a “2-3-3-2” ridge/surface grip pattern—isused on several devices manufactured and distributed by UniversalEnterprises, Inc. The 2-3-3-2 pattern is preferably repeated on bothleft and right sides. As shown, the 2-3-3-2 ridge/surface grip patterncomprises a left side pattern—two ridges 46, a larger section 34, threeridges 48, a large section 36, three ridges 50, a large section 38, andfinally two ridges 60—and a corresponding and matching right sidepattern—two ridges 52, a larger section 40, three ridges 54, a largesection 42, three ridges 56, a large section 44, and finally two ridges58.

The cutaway side view of the gas leak detector 10 in FIG. 3 depicts thedevice 10 having a longitudinal length from a bottom surface 24 to a topsurface 22, and a thickness from a front surface 68 to a back surface66. In preferred embodiments, a flexible tube 130 provides an airpassage from the intake probe 100 to the bench and pump componentswithin the space 70, the space 70 preferably positioned just aft of theintake probe 100 toward the back side of the main body. The bench andpump space 70 preferably has approximate dimensions 2.25″×3.625″×0.75″.Preferably below the bench and pump space 70 is a space for thebatteries 64, and the main circuit board 62 is positioned in front ofthe bench and pump space 70 and batteries 64. The main circuit board 62,in one embodiment, is approximately 2.25″×6.25″. Preferably in front ofthe main circuit board 62 opposite the bench and pump space 70 is adisplay or LED inset 12, and in front of the main circuit board 62opposite the bench and pump space 70 and positioned in the centralportion of the front side of the device 10, are the navigation buttons14.

Turning back to FIG. 4, the detailed components and operation of the gasdetector 10 may be different in various embodiments. The followingprovide additional details for the components diagrammed in FIG. 4,according to various embodiments.

The intake probe 100 may be flexible or rigid, and is for drawing in theair being tested. The intake probe 100 preferably extends outward fromthe top surface 22 of the main body of the leak detector 10. Preferablya filter protects the optics within the bench from liquids and dust. Theinventor discovered the IR detector works best when the tip of theintake probe 100 is used in a sweeping motion to test an area for a gasleak, the tip passing from clear air to contaminated air.

The air pump 120, in preferred embodiments, is used to draw air inthrough the intake probe 100, through a flexible hose 130, and throughthe sample tube 140. Suction provided by the air pump 120 draws in anair sample from an area suspected of leaking gas, at a rate that, as theinventor discovered, maximizes the response of the IR sensor 160 to thestep change in incident IR radiation that occurs when the sample air iscontaminated by a hazardous gas.

Preferably, a flexible hose 130 connects the intake probe 100 with theoptical bench. As shown, a flexible hose 130 connects the intake probe100 to an inlet of the sample tube 140 near the IR emitter 150, andanother flexible hose 130 connects the pump 120 to an outlet of thesample tube 140 near the IR sensor 160.

The sample tube 140 is preferably a small diameter tube that containsthe IR energy and allows the IR energy to interact with the air sample.The inventor discovered, contrary to some teachings, a highly polishedfinish inside the sample tube 140 is not required due to the short pathlength within the sample tube 140. The sample tube 140 is preferablyconfigured with an inlet located at the IR emitter 150 end of the sampletube 140, and an outlet located at the IR detector 160 end of the sampletube 140.

The IR emitter module 150 preferably comprises a resistive IR generatorcoupled through a wide band IR filter 190 to one end of the sample tube140. The IR emitter 150 is preferably highly insulated and allows themaximum IR energy to interact with the air sample. The IR emitter 150 ispreferably thermally isolated from the gas stream convection via thesingle wide band filter 190. In preferred embodiments, the IR emitter150 comprises a resistor that is heated to generate infrared (IR)emissions in the 0.4 to 20 um wavelength range, and the voltage thatdrives the IR emitter 150 is regulated, unlike teachings in other patentdisclosures. Additionally, the IR emitter 150 may have an integralthermistor for feedback to the regulator, to allow for consistentheating regardless of the ambient temperature.

The IR detector/sensor module 160 preferably comprises a highlysensitive commercially available IR sensor such as a thermopile or apyro-electric detector, and is positioned at the opposite end of thesample tube 140, opposite from the IR emitter 150. The IRdetector/sensor module 160 is preferably highly insulated from ambientair and the air sample. The IR sensor is preferably thermally isolatedfrom the gas stream convection via two IR filters 170, 180. The outputof the IR sensor 160, the inventor discovered, will drift due to heattransfer from the air flow in the sample tube. This drift, the inventordetermined, may be reduced by careful insulation of the optical benchand is thereafter of no consequence and may be ignored. The IR sensor160 responds to a change in the receive amount of IR radiation andproduces a proportional output signal.

DC coupled buffer electronics are preferably included (co-located withthe IR sensor 160) to reduce the output impedance of the IR sensor 160(to provide a low impedance drive to the analog to digital converter200), and the analog to digital converter 200 may also be co-locatedwith the IR sensor 160.

An optional version of the IR sensor module 160 incorporates either dualor quad IR sensors in one package, with each independent sensor/detectorhaving a unique IR filter 170.

The filter 170 shown as “Filter 1” in FIG. 4 is preferably physicallyinsulated from both “Filter 2” 180 and the IR detector 160 to minimizeheat transfer from the air sample, and may be a wide band 0.4 to 20micrometer wavelength filter for general hazardous gas detection, oroptimized to detect a specific gas. In preferred embodiments, the IRfilter 170 is integral with the IR sensor 160 package (or multipleunique IR filters are integral with the IR sensor package if dual orquad sensors are used).

The filter 170 may be a wide band or a narrow band filter depending uponthe application. Other IR gas leak detector related patent disclosuresspecifically exclude the band of IR wavelengths between 0.4 and 6 um(microns or micrometers), which means those leak detector designs, theinventor determined, cannot detect methane, carbon monoxide (CO), andcarbon dioxide (CO2). Preferably the gas leak detector 10 comprises awide band hazardous gas detector and is capable of detecting many gases.

Alternately, if CO2 or CO is the desired gas, or both gases, the filter170 passes wavelengths in the range 4-5 um. If a methane detector isdesired, the filter centers on approximately 3.3 um.

The filter 180 shown as “Filter 2” is preferably physically insulatedfrom “Filter 1” 170 to minimize heat transfer from the air sample, andmay be a wide band 0.4 to 20 micrometer wavelength filter for generalhazardous gas detection or optimized to detect a specific desired gas.Filter 180 preferably precedes the IR sensor 160 and may be either awide band or narrow band filter depending upon the application.

The filter 190 shown as “Filter 3” is preferably a wide band passing 0.4to 20 micrometer wavelength filter, and positioned to insulate the IRemitter 150 from the air sample. The wide band filter 190, the inventordiscovered, provides temperature insensitivity.

In one embodiment, only one filter, Filter 1 170, is used, and the othertwo filters (Filter 2 180 and Filter 3 190) are not included in the leakdetector 10; and the filter 170 comprises an IR band pass filter thatallows passage of IR wavelengths within the range of approximately 0.4um to approximately 20 um. The inventor determined this embodiment(having only one IR band pass filter 170) to be a lower cost version andmost suitable for detection of inert gases such as CO2.

In a second embodiment, only two filters, Filter 1 170 and Filter 3 190,are used, and the other filter shown in FIG. 4 (Filter 2 180) is notincluded in the leak detector 10. The inventor determined thisembodiment (having two band pass filters 170, 190 with one in front ofthe IR emitter 150 and the other in front of the IR sensor 160, and eachfilter allowing passage of IR energy within the range of 0.4 um to 20um) to be effective for hazardous leak detection.

In a third embodiment, all three of the filters shown in FIG. 4, Filter1 170, Filter 2 180, and Filter 3 190, are used as previously described;and in this embodiment, Filter 3 190 may be selected with a narrowerband to detect a specific gas or gases.

The analog to digital conversion 200 preferably comprises a highresolution analog to digital converter (ADC) that is DC coupled to theIR sensor 160 output, and in preferred embodiments it is not necessaryto zero, accumulate, or hold the signal. Preferably, the leak detector10 circuitry does not “accumulate” the signal, instead utilizing ananalog to digital converter to provide continuous real-time sampling ofthe signal from the IR sensor 160 so that the device 10 does not have orrequire any analog accumulation or forward biased detector circuit.Moreover, a zero circuit is not necessary or included. A digital toanalog converter is used to softly keep the signal in the lineardetecting range of the ADC; detection occurs when the digital value ofthe signal makes a more rapid change than the normal thermal drift ofthe IR sensor 160, caused by the change in concentration of a detectablegas. Conversion of IR energy to kinetic energy by the gas compounds thatare drawn through the sample tube 140 and the subsequent reduction in IRenergy, is detected by the IR sensor 160 and converted to a digitalvalue by the high resolution ADC 200.

The CPU or microcontroller or microprocessor 210 is preferablyconfigured to discriminate the digitized signal received from the ADC200. The digital signal from the ADC 200 is preferably evaluated by themicroprocessor 210, and the processor 210 reacts to the signals based ona discrimination algorithm. Preferably, the normal slower drift of theIR sensor 160 is ignored and a rapid reduction of the IR at the sensor160, due to gas absorbing the IR energy in the sample air, is designatedas a valid gas detection. Preferably software determines the size of thegas leak detected and in the case of multiple detectors, what band thedetected gas resides in. An example is a hazardous gas detector thatdetects methane, carbon dioxide, carbon monoxide, and one of severalrefrigerants.

The power, battery, and charging 220 preferably includes various voltageregulators to provide power to the gas leak detector 10. Themicroprocessor 210 preferably monitors the battery charge condition.

The indicators 300 preferably comprise LED or LDC display indicators ofthe condition and operating state of the leak detector 10, an indicationof the magnitude of the signal, indicators to indicate if the detectoris in the measure of locate mode, as well as a low battery indication.The indicators 300 preferably comprise a speaker to provide a three toneidle signal every two seconds when the unit is not detecting a hazardousgas. When a gas is detected, the indicator changes to a high pitchsqueal, with the frequency increasing with increased gas concentrationdetection. A non-detection operation is preferably indicated by a threetone “doo-dee-doo” every two seconds. This indicates the device 10 iswarming up and operating. The three tone indication preferably changesto a high pitched squeal of 2000 Hz and up upon detection of adetectable gas, the audible signal comprising a tone and not a chirp.The indicators 300 preferably further comprise a vibrator for a tactileindication of a sensing event, with the intensity increasing relative tothe concentration of the gas. The tactile indication is useful when theindicators cannot be seen or heard.

The volume and sensitivity control 310 preferably comprises volumecontrol via short activations of the on/off button. Preferably theon/off function is by way of holding the button for three seconds. Insome embodiments, there are two sensitivity adjustment controls. Onebutton causes the detector PG2 to step through predetermined detectionwindows. The other sensitivity control places the hazardous gas detector10 in the “Locate” mode and significantly increases the sensitivity sothat the unit 10 can “sniff” for low concentrations of gas. Preferablyan indicator lights to indicate the mode of operation. In preferredembodiments, four buttons control the device 10—power on/off,sensitivity control, mute on/off, and peak hold.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention in the use of such terms andexpressions of excluding equivalents of the features shown and describedor portions thereof, it being recognized that the scope of the inventionis defined and limited only by the claims which follow.

What is claimed is:
 1. A single-hand operable, single-hand sized,handheld portable gas leak detector comprising: (a) a single-hand sizedhousing enclosure having an interior volume and having a length, awidth, and a thickness, the length extending longitudinally from abottom surface to a top surface, the width extending from a left sidesurface to a right side surface, and the thickness extending from a backside surface to a front side surface; (b) an intake probe tube extendingaway from the interior of the housing enclosure; (c) an optical benchdisposed within said housing enclosure that includes an air sample tubehaving an infrared (IR) emitter module at one end of the air sample tubeand an IR sensor module at the opposite end of the air sample tube, aninlet near said IR emitter module fluidly connected with said intakeprobe tube, and an outlet near said IR sensor module fluidly connectedwith an air pump within said housing enclosure via a flexible tube, saidoptical bench being insulated from bending within said housingenclosure; (d) said IR sensor module having a wide band optical filteroriented between air drawn in to said air sample tube and an IR sensorwithin said IR sensor module; (e) an analog to digital converter (ADC)electrically interconnected with said IR sensor module; (f) amicroprocessor (CPU) electrically interconnected with said ADC andadapted for performing an algorithm that triggers detection of a gaswhen a change in IR energy between said IR emitter module and said IRsensor module is more rapid than a thermal drift of said IR sensormodule; and (g) a battery power supply electrically interconnected withsaid CPU, said ADC, said air pump, said IR emitter module, and said IRsensor module.
 2. The detector of claim 1 wherein said length is greaterthan said width and said width is greater than said thickness, whereinsaid intake probe tube is flexible and includes a moisture filter, andwherein said air pump draws air at a rate of approximately 100cc/minute.
 3. The detector of claim 1 wherein said optical benchcomprises just one optical filter consisting of said wide band opticalfilter, said wide band optical filter allowing passage of IR wavelengthswithin the range of approximately 0.4 um to approximately 20 um andattenuating IR wavelengths outside of that range.
 4. The detector ofclaim 1 wherein said optical bench comprises just two optical filtersconsisting of said wide band optical filter, said wide band opticalfilter allowing passage of IR wavelengths within the range ofapproximately 0.4 um to approximately 20 um and attenuating IRwavelengths outside of that range, and a second wide band optical filterpositioned between air drawn in to said air sample tube and the IRemitter in said IR emitter module, said second wide band optical filterallowing passage of IR wavelengths within the range of approximately 0.4um to approximately 20 um and attenuating IR wavelengths outside of thatrange.
 5. The detector of claim 1 wherein said optical bench comprisesjust three optical filters consisting of said wide band optical filteras a first optical filter, said first optical filter allowing passage ofIR wavelengths within the range of approximately 0.4 um to approximately20 um and attenuating IR wavelengths outside of that range, and a secondoptical filter positioned between air drawn in to said air sample tubeand the IR emitter in said IR emitter module, said second optical filterallowing passage of IR wavelengths within the range of approximately 0.4um to approximately 20 um and attenuating IR wavelengths outside of thatrange, and a third optical filter positioned between air drawn in tosaid air sample tube and said first optical filter, said third opticalfilter allowing passage of a narrow band of IR wavelengths to detect aspecific gas and attenuating IR wavelengths outside of that range. 6.The detector of claim 1 further comprising a speaker that provides athree tone idle signal every two seconds when not indicating detectionof a target gas and that provides a high pitch squeal when indicatingdetection of said target gas, with the frequency of the squealincreasing with detection of increased concentration of said target gas,a visual display that provides a light when indicating detection of saidtarget gas, with an increase in an amount of said light with detectionof increased concentration of said target gas, and a tactile indicationthat provides a vibration with detection of said target gas, with anincrease in vibration intensity with detection of increasedconcentration of said target gas.
 7. The detector of claim 1 whereinsaid optical bench is insulated from bending by using a floatingmounting of said bench whereby a space within which said bench isdisposed is floatably secured within said housing such that distortionsto said housing do not transfer to distortions of said space.
 8. Thedetector of claim 1 wherein said optical bench is insulated from bendingby being molded into molded structure comprising said housing enclosure.9. A single-hand operable, single-hand sized, handheld portable gas leakdetector comprising: (a) a single-hand sized housing enclosure having aninterior volume and having a length, a width, and a thickness, thelength extending longitudinally from a bottom surface to a top surface,the width extending from a left side surface to a right side surface,and the thickness extending from a back side surface to a front sidesurface, wherein said length is greater than said width and said widthis greater than said thickness; (b) an intake probe tube extending awayfrom the interior of the housing enclosure, wherein said intake probetube includes a moisture filter; (c) an optical bench disposed withinsaid housing enclosure that includes an air sample tube having aninfrared (IR) emitter module at one end of the air sample tube and an IRsensor module at the opposite end of the air sample tube, an inlet nearsaid IR emitter module fluidly connected with said intake probe tube,and an outlet near said IR sensor module fluidly connected with an airpump within said housing enclosure via a flexible tube, said opticalbench being insulated from bending within said housing enclosure,wherein said air pump draws air at a rate of approximately 100cc/minute; (d) said IR sensor module having a wide band optical filteroriented between air drawn in to said air sample tube and an IR sensorwithin said IR sensor module; (e) an analog to digital converter (ADC)electrically interconnected with said IR sensor module; (f) amicroprocessor (CPU) electrically interconnected with said ADC andadapted for performing an algorithm that triggers detection of a gaswhen a change in IR energy between said IR emitter module and said IRsensor module is more rapid than a thermal drift of said IR sensormodule; (g) a battery power supply electrically interconnected with saidCPU, said ADC, said air pump, said IR emitter module, and said IR sensormodule; (h) a speaker that provides a three tone idle signal every twoseconds when not indicating detection of a target gas and that providesa high pitch squeal when indicating detection of said target gas, withthe frequency of the squeal increasing with detection of increasedconcentration of said target gas; (i) a visual display that provides alight when indicating detection of said target gas, with an increase inan amount of said light with detection of increased concentration ofsaid target gas; and (j) a tactile indication that provides a vibrationwith detection of said target gas, with an increase in vibrationintensity with detection of increased concentration of said target gas.10. The detector of claim 9 wherein said intake probe tube is flexible.11. The detector of claim 9 wherein said intake probe tube is rigid. 12.The detector of claim 9 wherein said optical bench comprises just oneoptical filter consisting of said wide band optical filter, said wideband optical filter allowing passage of IR wavelengths within the rangeof approximately 0.4 um to approximately 20 um and attenuating IRwavelengths outside of that range.
 13. The detector of claim 9 whereinsaid optical bench comprises just two optical filters consisting of saidwide band optical filter, said wide band optical filter allowing passageof IR wavelengths within the range of approximately 0.4 um toapproximately 20 um and attenuating IR wavelengths outside of thatrange, and a second wide band optical filter positioned between airdrawn in to said air sample tube and the IR emitter in said IR emittermodule, said second wide band optical filter allowing passage of IRwavelengths within the range of approximately 0.4 um to approximately 20um and attenuating IR wavelengths outside of that range.
 14. Thedetector of claim 9 wherein said optical bench comprises just threeoptical filters consisting of said wide band optical filter as a firstoptical filter, said first optical filter allowing passage of IRwavelengths within the range of approximately 0.4 um to approximately 20um and attenuating IR wavelengths outside of that range, and a secondoptical filter positioned between air drawn in to said air sample tubeand the IR emitter in said IR emitter module, said second optical filterallowing passage of IR wavelengths within the range of approximately 0.4um to approximately 20 um and attenuating IR wavelengths outside of thatrange, and a third optical filter positioned between air drawn in tosaid air sample tube and said first optical filter, said third opticalfilter allowing passage of a narrow band of IR wavelengths to detect aspecific gas and attenuating IR wavelengths outside of that range. 15.The detector of claim 9 wherein said optical bench is insulated frombending by using a floating mounting of said bench whereby a spacewithin which said bench is disposed is floatably secured within saidhousing such that distortions to said housing do not transfer todistortions of said space.
 16. The detector of claim 9 wherein saidoptical bench is insulated from bending by being molded into moldedstructure comprising said housing enclosure.
 17. A single-hand operable,single-hand sized, handheld portable gas leak detector comprising: (a) asingle-hand sized housing enclosure having an interior volume and havinga length, a width, and a thickness, the length extending longitudinallyfrom a bottom surface to a top surface, the width extending from a leftside surface to a right side surface, and the thickness extending from aback side surface to a front side surface; (b) an intake probe tubeextending away from the interior of the housing enclosure, wherein saidintake probe tube includes a moisture filter; (c) an optical benchdisposed within said housing enclosure that includes an air sample tubehaving an infrared (IR) emitter module at one end of the air sample tubeand an IR sensor module at the opposite end of the air sample tube, aninlet near said IR emitter module fluidly connected with said intakeprobe tube, and an outlet near said IR sensor module fluidly connectedwith an air pump within said housing enclosure via a flexible tube, saidoptical bench being insulated from bending within said housingenclosure; (d) said IR sensor module having a wide band optical filteroriented between air drawn in to said air sample tube and an IR sensorwithin said IR sensor module; (e) an analog to digital converter (ADC)electrically interconnected with said IR sensor module; (f) amicroprocessor (CPU) electrically interconnected with said ADC andadapted for performing an algorithm that triggers detection of a gaswhen a change in IR energy between said IR emitter module and said IRsensor module is more rapid than a thermal drift of said IR sensormodule; and (g) a battery power supply electrically interconnected withsaid CPU, said ADC, said air pump, said IR emitter module, and said IRsensor module; (h) a speaker that provides a three tone idle signalevery two seconds when not indicating detection of a target gas and thatprovides a high pitch squeal when indicating detection of said targetgas, with the frequency of the squeal increasing with detection ofincreased concentration of said target gas; (i) a visual display thatprovides a light when indicating detection of said target gas, with anincrease in an amount of said light with detection of increasedconcentration of said target gas; and (j) a tactile indication thatprovides a vibration with detection of said target gas, with an increasein vibration intensity with detection of increased concentration of saidtarget gas, wherein said optical bench comprises just three opticalfilters consisting of said wide band optical filter as a first opticalfilter, said first optical filter allowing passage of IR wavelengthswithin the range of approximately 0.4 um to approximately 20 um andattenuating IR wavelengths outside of that range, and a second opticalfilter positioned between air drawn in to said air sample tube and theIR emitter in said IR emitter module, said second optical filterallowing passage of IR wavelengths within the range of approximately 0.4um to approximately 20 um and attenuating IR wavelengths outside of thatrange, and a third optical filter positioned between air drawn in tosaid air sample tube and said first optical filter, said third opticalfilter allowing passage of a narrow band of IR wavelengths to detect aspecific gas and attenuating IR wavelengths outside of that range. 18.The detector of claim 17 wherein said intake probe tube includes amoisture filter, and wherein said air pump draws air at a rate ofapproximately 100 cc/minute.
 19. The detector of claim 17 wherein saidoptical bench is insulated from bending by using a floating mounting ofsaid bench whereby a space within which said bench is disposed isfloatably secured within said housing such that distortions to saidhousing do not transfer to distortions of said space.
 20. The detectorof claim 17 wherein said optical bench is insulated from bending bybeing molded into molded structure comprising said housing enclosure.